The structural health monitoring (SHM) field often aims at carrying out the diagnostics and monitoring of structures using sensor (commonly, transducer) arrays connected to associated hardware, such as dedicated analyzers. When connected to a computer, this hardware can allow users to determine the integrity of structures, often in, or close to, real time. In this manner, SHM systems and techniques can go beyond simple detection of structural failure, to providing additional useful information such as early indications of damage.
However, SHM systems still suffer from drawbacks. For example, it is often desirable to configure SHM systems with both “active” and “passive” components. The active components transmit excitation signals to the transducers, generating diagnostic stress waves in the structure being monitored. These waves are picked up by neighboring sensors, and the resulting signals are analyzed to determine the health of the structure. In some approaches, differences between the signals sent to the transducers and those received back from other sensors, or differences between received signals and a stored set of baseline data, can indicate damage to the structure.
In contrast, the passive components are not used to generate such interrogating waveforms. Rather, they passively monitor the structure, “listening” to detect stress waves generated in the structure by some event (e.g., an impact, or operation of the structure). When stress waves exceeding a specified threshold are detected, the system records/analyzes them to determine information such as whether an impact occurred, its location, and force.
It is often desirable to utilize both passive and active components in a single SHM system. In such cases, it is further desirable to use the same transducers (i.e., sensors/actuators) for both active sensing and passive sensing. This typically entails connecting both the passive and active components to the same transducers, which also means that both the passive and active components are electrically connected to each other. However, such configurations currently face significant challenges. For example, excitation signals from active components are often high voltage signals, and must be blocked from the passive system so as to avoid damaging the sensitive circuitry of the passive system with excessively large voltage pulses.
Such blocking is often accomplished via high-voltage switches placed between the transducers and passive system circuitry, with the switches being opened during operation of the active system so that the passive system is disconnected from the active system during operation of the active system. However, as a separate switch is often desired for each transducer, large transducer arrays can often require big, bulky banks of switches that can be complicated and expensive to implement. Additionally, the switches are often operated via custom software that must be written, adding to time and expense.